The present invention relates to an ink for ink jet recording, a process for the preparation thereof, an ink set for ink jet recording, and an ink cartridge.
More particularly, the present invention relates to an ink for ink jet recording comprising at least a particulate pigment having a sulfur-containing dispersibility providing group chemically bonded to the surface thereof with a treatment containing sulfur, a penetrating agent, and water, characterized by the following aspects:
(a) An ink for ink jet recording wherein the sulfur content in the liquid component of the ink is kept to a predetermined level or less (hereinafter referred to as xe2x80x9cfirst ink of the inventionxe2x80x9d);
(b) An ink for ink jet recording wherein the amount of the sulfur-containing dispersibility providing group is kept to a predetermined value or more (hereinafter referred to as xe2x80x9csecond ink of the inventionxe2x80x9d) and a process for the preparation thereof;
(c) An ink for ink jet recording wherein the sulfur-containing dispersibility providing group is a predetermined ion group and the cation as its counter ion is predetermined (hereinafter referred to as xe2x80x9cthird ink of the inventionxe2x80x9d) and a process for the preparation thereof;
(d) An ink for ink jet recording comprising a specific preservative incorporated therein (hereinafter referred to as xe2x80x9cfourth ink of the inventionxe2x80x9d); and
(e) An ink for ink jet recording comprising a predetermined penetrating agent incorporated therein (hereinafter referred to as xe2x80x9cfifth ink of the inventionxe2x80x9d).
The present invention further relates to an ink set for ink jet recording comprising the foregoing first and second inks of the invention. The present invention still relates to an ink cartridge for ink jet recording apparatus.
(Prior Art Concerning Ink)
As a colorant to be incorporated in an ink for ink jet recording there has heretofore been mainly used a dye. The use of a dye, which exhibits an excellent fastness, has recently been studied.
A pigment is superior to a dye in respect to fastness such as water resistance and light-resistance. However, since a pigment cannot be dissolved in water unlike a dye, it is important for pigment ink to allow the pigment to be finely dispersed in water in a stable manner. Further, when a penetrating agent is incorporated in a pigment ink for the purpose of enhancing the penetrating power of the ink, the dispersion stability of the particulate pigment is remarkably impaired, making it impossible to secure the ink with a desired storage stability.
As a method for rendering the surface of a particulate pigment wettable with water to prevent the agglomeration and precipitation of pigment particles, it has been practiced to disperse pigment particles in an aqueous solvent with a dispersant such as various surface active agents and aqueous resins. For examples, JP-A-3-157464 (The term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) gives a study of a pigment ink comprising an acetylene glycol-based penetrating agent incorporated therein wherein as a dispersant for particulate pigment there is used a polymer dispersant and as an aqueous medium there is used water, nonvolatile organic solvent or lower alcohol to secure the dispersion stability thereof. However, when a dispersant is thus used for particulate pigment, the preparation of the ink requires more factors, making it difficult to allow desired design of ink physical properties such as viscosity. With this pigment ink, too, the foregoing problem that desired print density can be hardly secured is left unsolved.
As another method for dispersing a pigment in water there has been proposed a technique involving the introduction of sulfonic acid group onto the surface of a particulate pigment. For example, JP-A-10-110129 discloses a recording solution for ink jet recording comprising a sulfonated surface-treated organic pigment obtained by treating with a sulfonating agent an organic pigment dispersed in a solvent free of active proton. The above cited patent application discloses that the foregoing recording solution for ink jet recording has a stable dispersibility and thus can be securely ejected from the nozzle. Further, JP-A-11-49974 discloses that an organic bulk pigment which can be positively charged on the surface thereof is prepared by treating an organic bulk pigment having a sulfonic acid group introduced therein with a monovalent metal ion. The above cited patent application also discloses an aqueous ink composition which comprises a particulate pigment prepared from the surface positively chargeable organic bulk pigment, a dispersant and water and thus exhibits an excellent storage stability.
The inks comprising a surface-treated particulate pigment proposed in the foregoing two patent applications can satisfy various requirements as compared with the conventional pigment-based ink jet recording inks but leave something to be desired in storage stability because they comprise various components incorporated therein in combination to have desired print quality and dryability.
On the other hand, an ink for ink jet printer is required to meet various physical properties. In particular, it is important to secure desired storage stability and ejection stability (prevention of dot drop and clogging). Further, printing on recording paper is required to meet the following requirements (1) to (3):
(1) The printed image has little irregular bleeding;
(2) The image which has been printed can rapidly dry; and
(3) The printed image has a high print density.
In order to meet the foregoing requirements (1) to (3), various studies have long been made. For example, an approach involving the enhancement of the penetrating power of an ink for the purpose of eliminating bleeding on printed image and improving the dryability of printed image has been studied. U.S. Pat. No. 5,156,675 proposes the use of diethylene glycol monobutyl ether. U.S. Pat. No. 5,183,502 proposes the use of an acetylene glycol-based surface active agent.
However, the foregoing ink which comprises such a penetrating agent incorporated therein to have a drastically improved penetrating power is disadvantageous in that the colorant, too, penetrates deep into the recording paper, making it difficult to secure the printed image with a desired print density.
It has thus been desired to provide an ink for ink jet printer which can meet not only the foregoing requirements for physical properties, particularly storage stability and ejection stability (prevention of dot drop and clogging) but also the foregoing requirements (1) to (3).
(Prior Art Concerning Ink, Particularly Penetrating Agent)
An ink to be used in ink jet recording is required to meet requirements that the printed matter thus obtained dry fairly dry and show no bleeding, the ink can be printed uniformly on the surface of all recording media and a plurality of colors, if any, be not mixed. A particular problem that can occur is that when paper is used as a recording medium, the ink can undergo bleeding with fibers having different penetrabilities.
The most conventional inks for ink jet recording comprise glycol ether incorporated therein as a wetting agent as disclosed in JP-B-2-2907 (The term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent applicationxe2x80x9d), comprise a water-soluble organic solvent as disclosed in JP-B-1-15542 or comprise a dye dissolution accelerator incorporated therein as disclosed in JP-B-2-3837.
In order to enhance penetrating power, the addition of diethylene glycol monobutyl ether has been studied as disclosed in U.S. Pat. No. 5,156,675, the addition of Surfynol 465 (produced by Air Products Co., Ltd.), which is an acetylene glycol-based surface active agent, has been studied as disclosed in U.S. Pat. No. 5,183,502, and the addition of both diethylene glycol monobutyl ether and Surfynol 465 has been studied as disclosed in U.S. Pat. No. 5,196,056. Diethylene glycol mono-n-butyl ether is called xe2x80x9cbutyl carbitolxe2x80x9d and is disclosed in, e.g., U.S. Pat. No. 3,291,580. Further, U.S. Pat. No. 2,083,372 give a study of the use of ethers such as diethylene glycol as an ink.
Most inks comprising a pigment are mainly arranged to have a lowered penetrating power that prevents themselves from wetting the surface of paper to secure desired print quality. These inks have been put to practical use. Further, an ink comprising triethylene glycol monomethyl ether incorporated therein as a pigment has been proposed as disclosed in JP-A-56-147861. An ink comprising an ether such as ethylene glycol, diethylene glycol and triethylene glycol incorporated therein as a pigment has been proposed as disclosed in JP-9-111165.
(Prior Art Concerning Ink Set)
An ink jet recording method is a printing method which comprises allowing a droplet of ink composition to fly and adhere to a recording medium such as paper to effect printing. In accordance with this printing method, a high resolution and fidelity image can be printed at a high speed using a relatively inexpensive apparatus.
As an ink jet recording method there has recently been proposed a method which comprises applying a polyvalent metal salt solution to a recording medium, and then applying an ink composition comprising a dye material having at least one carboxyl group thereto (as disclosed in JP-A-5-202328). It is proposed that this ink jet recording method allows the formation of an insoluble composite from a polyvalent metal ion and a dye and the presence of the composite makes it possible to obtain a high fidelity water-resistant image free from color bleeding.
It has also been proposed that the combined use of at least a surface active agent or penetrating solvent for providing penetrating power, a color ink containing a salt, and a black ink which undergoes thickening or agglomeration when acted upon by the salt makes it possible to obtain a high fidelity color image having a high image density free from color bleeding (as disclosed in JP-A-6-106735). In other words, an ink jet recording method has been proposed which comprises printing two solutions, i.e., first solution containing a salt and ink composition to obtain a good image.
The recent trend of an ink jet recording method is that a plurality of color ink compositions are subjected to ink jet recording to form a color image. In general, a color image is formed by three color ink compositions, i.e., yellow ink composition, magenta ink composition and cyan ink composition, optionally four color ink compositions, i.e., black ink composition in addition to the foregoing three color ink compositions.
An ink composition to be used in the formation of such a color image is required to have a good color developability itself as well as allow the development of a good half tone color when combined with a plurality of ink compositions.
(Prior Art Concerning Ink Cartridge)
In a printer such as ink jet printer, an ink cartridge is used to feed the ink to the printer. Such an ink cartridge comprises a porous material impregnated with an ink received in a case.
A porous material to be impregnated with an ink often has various reactive materials or impurities attached thereto or left therein. Accordingly, when such a porous material is impregnated with an ink, the reactive materials or impurities in the porous material are eluted with the ink to change the composition of the ink or act with the ingredients in the ink. The resulting crystal can have adverse effects on the printing characteristics. For example, a polyurethane foam which is widely used as an ink impregnating porous material is prepared in the presence of an organic metal compound (e.g., organic tin compound) as a catalyst. Accordingly, when the polyether urethane foam comes in contact with an ink, the organic metal compound is eluted with the ink to undergo recrystallization in the ink. The organic metal compound thus recrystallized adheres to the inner surface of the nozzle. This causes the ink thus ejected to fry in a deviated direction or the ink to clog the nozzle.
It has thus been desired to develop an ink for ink jet recording which meets the foregoing physical properties, particularly desired storage stability and ejection stability, and the foregoing requirements (1) to (3) at the same time and an ink cartridge which causes substantially no change of these physical properties and printing properties of ink for ink jet printer.
(Problems that the Invention is to Solve]
The inventors made extensive studies of requirements for the foregoing ink for ink jet printer, ink set for ink jet printer and ink cartridge. As a result, a specific particulate pigment having a sulfur-containing dispersibility providing group chemically bonded to the surface thereof with a treatment containing sulfur was developed. Thus, the present invention has been worked out. Objects (problems) of the invention will be described in detail with reference to roughly divided aspects, i.e., xe2x80x9cink for ink jet recording (first to fourth inks of the invention)xe2x80x9d, xe2x80x9cink for ink jet recording (fifth ink of the inventionxe2x80x9d, xe2x80x9cink set for ink jet recordingxe2x80x9d and xe2x80x9cink cartridgexe2x80x9d according to the invention.
 less than Object (Problem) of Ink for Ink Jet Recording (First to Fourth Inks of the Invention) According to the Invention greater than 
The inventors made extensive studies of an ink which satisfies the foregoing ink physical properties and printing properties required for ink for ink jet recording at the same time. As a result, it was found that the ink which satisfies the foregoing ink physical properties and printing properties at the same time can be realized by an ink for ink jet recording comprising at least a particulate pigment having a sulfur-containing dispersibility providing group chemically bonded to the surface thereof with a treatment containing sulfur, a penetrating agent, and water, characterized by the following aspects:
(a) An ink for ink jet recording wherein the sulfur content in the liquid component of the ink is kept to a predetermined level or less (hereinafter referred to as xe2x80x9cfirst ink of the inventionxe2x80x9d);
(b) An ink for ink jet recording wherein the amount of the sulfur-containing dispersibility providing group is kept to a predetermined value or more (hereinafter referred to as xe2x80x9csecond ink of the inventionxe2x80x9d) and a process for the preparation thereof;
(c) An ink for ink jet recording wherein the sulfur-containing dispersibility providing group is a predetermined ion group and the cation as its counter ion is predetermined (hereinafter referred to as xe2x80x9cthird ink of the inventionxe2x80x9d) and a process for the preparation thereof; and
(d) An ink for ink jet recording comprising a specific preservative incorporated therein (hereinafter referred to as xe2x80x9cfourth ink of the inventionxe2x80x9d).
The ink for ink jet recording (first to fourth inks of the invention) according to the invention is based on the foregoing knowledge. An object of the invention is to provide a pigment ink for ink jet recording (first to fourth inks of the invention) excellent in fastness (light-resistance, water resistance, etc.), characterized in that the foregoing requirements for ink for ink jet recording can be satisfied at the same time while securing the desired storage stability of the ink:
(1) Little irregular bleeding on the printed matter;
(2) The image which has been printed can rapidly dry;
(3) The printed image has a high print density;
(4) The ink is provided with an excellent storage stability; and
(5) The ink can be easily prepared.
 less than Object (Problem) of Ink for Ink Jet Recording (Fifth Ink of the Invention) According to the Invention greater than 
As previously described in the clause xe2x80x9c(Prior art concerning ink: mainly concerning penetrating agent)xe2x80x9d, the penetrating properties of an ink has been studied. Most of the prior art inks leave something to be desired. In the case where a method involving the inhibition of wetting on the surface of paper is used, the prior art inks bleed over ordinary paper, particularly regenerated paper, which is often used, and thus take much time to dry. Accordingly, when printed continuously, the ink which has been printed on paper can difficultly dry, making it impossible to allow immediate printing thereon. Regenerated paper is a mixture of various paper components and thus is an aggregate of paper components having different penetrabilities. The difference in penetrability between paper components makes it easy for the ink to bleed.
An ink comprising a pigment is disadvantageous in that when printed on, e.g., a paper containing an ordinary sizing agent as a recording medium, the pigment is left behind on the surface of paper or the like, accelerating fretting, unless the ink is provided with some penetrating power. However, when the penetrating power thus provided is insufficient, the kind of the paper to be used must be restricted or the quality of printed image can be deteriorated. Further, most inks comprising a pigment comprise a methyl ether as used in JP-A-56-147851 as a glycol ether for controlling the penetrating powder thereof. No pigment-based inks for ink jet recording which can exhibit a penetrating power improved with butyl ethers to print on various papers with little bleeding have been known.
The fifth ink of the invention gives solution to these problems. An object (problem) of the invention is to provide an ink for ink jet recording which can penetrate very rapidly into ordinary paper and regenerated paper or coated paper, which is widely used in recent years, to print with little bleeding and a high print quality.
 less than Object (Problem) of Ink Set for Ink Jet Recording According to the Invention greater than 
In the case where as a coloring agent for ink there is used a pigment, different pigments give different surface physical properties. In order to stabilize dispersion, the kind and added amount of the dispersant to be used must be properly changed depending on the kind of the pigment to be dispersed. Such a dispersion has the following disadvantages (problems) (6) and (7):
(6) Even if a pigment which can give a proper color reproduction range and a high saturation is selected as a coloring agent for ink, the resulting ink cannot exhibit physical properties desirable for ink jet recording. After all, the capability inherently given by the combination of pigments cannot be made the use of to disadvantage.
(7) Most inks for ink jet recording exhibit an enhanced penetrating power with respect to paper to accomplish the prevention of color bleeding. However, ink additives for providing paper with penetrating power occasionally cause the desorption of the dispersant from the pigment to produce aggregates or change the physical properties of the ink.
The inventors obtained knowledge that an ink for ink jet recording comprising a pigment as a coloring agent for ink can avoid the foregoing problems by using various pigments having the same surface conditions. The inventors obtained another knowledge that a specific combination of pigments can accomplish a good color image.
The ink set for ink jet recording according to the invention is based on the foregoing knowledge. Objects of the invention are as follows:
To provide an ink set for ink jet recording which allows optimization of pigment concentration, extremely easy design of pigment ink and development of desired half tone colors to attain a good color image;
To provide an ink set for ink jet recording which can comprise specific pigments in combination to attain a better color image, particularly a good hue; and
To provide an ink set for ink jet recording excellent in the stability of ink dispersion.
 less than Object (Problem) of Ink Cartridge According to the Invention greater than 
The inventors found that an ink for ink jet recording which can satisfy the foregoing ink physical properties and print properties at the same time can be realized by keeping the sulfur content in an ink containing various surface-treated particulate pigments to a predetermined level or less as in the foregoing first ink of the invention. The inventors also found that an excellent ink cartridge can be prepared by impregnating an ink impregnating foam with this ink.
The ink cartridge according to the invention is based on the foregoing knowledge. An object of the invention is to provide an excellent ink cartridge which can give desired storage stability and ejection stability (prevention of clogging) and maintain the print properties of the foregoing ink securely.
(Means for Solving the Problems)
 less than First Ink of the Invention greater than 
The first ink of the invention gives, as a technical constitution for accomplishing the foregoing xe2x80x9cobject (problem) of ink for ink jet recording (first to fourth inks of the invention) according to the inventionxe2x80x9d, an ink for ink jet recording comprising at least a particulate pigment having a sulfur-containing dispersibility providing group chemically bonded to the surface thereof with a treatment containing sulfur, a penetrating agent, and water, characterized in that the sulfur content in the liquid component of the ink is 2,000 ppm or less, preferably 1,000 ppm as calculated in terms of SO42xe2x88x92.
In a preferred embodiment of the first ink of the invention, the amount of polyvalent metal ions contained in the liquid component is 800 ppm or less. In another preferred embodiment of the first ink of the invention, the pigment is a carbon black pigment and/or organic pigment. In a further preferred embodiment of the first ink of the invention, the penetrating agent is an acetylene glycol-based surface active agent, acetylene alcohol-based surface active agent, 1,2-alkylene glycol and/or glycol ether.
A still further preferred embodiment of the first ink of the invention is an ink for ink jet recording further containing a material having a structure represented by the following general formula (1):
Rxe2x80x94EOn1xe2x80x94POm1xe2x80x94Xxe2x80x83xe2x80x83(1)
wherein R represents a C4-10 alkanol group which is an n-group and/or other isomers; EO represents an ethylene oxy group; PO represents a propylene oxy group, with the proviso that EO and PO are present in the molecule and their order of arrangement are arbitrary; X represents a hydrogen atom or xe2x80x94SO3M (in which M represents a hydrogen ion, alkaline metal, inorganic base or organic amine); and n1 and m1 each represent the number of repetition of EO and PO, respectively, which are each a value averaged over the entire system, i.e., from 0 to 10 and from 1 to 5, respectively.
A still further preferred embodiment of the first ink of the invention is an ink for ink jet recording further containing a particulate polymer. The added amount of the particulate polymer is preferably from 0.5 to 10% by weight.
 less than Second Ink of the Invention greater than 
The second ink of the invention gives, as a technical constitution for accomplishing the foregoing xe2x80x9cobject (problem) of ink for ink jet recording (first to fourth inks of the invention) according to the inventionxe2x80x9d, an ink for ink jet recording comprising at least a particulate pigment having a sulfur-containing dispersibility providing group chemically bonded to the surface thereof with a treatment containing sulfur, a penetrating agent, and water, characterized in that the amount of the sulfur-containing dispersibility providing group is 10xc3x9710xe2x88x926 equivalent or more per g of particulate pigment.
In a preferred embodiment of the second ink of the invention, the sulfur-containing dispersibility providing group is a sulfonic acid group (xe2x80x94SO2OH) and/or sulfinic acid group (xe2x80x94RSO2H in which R is a C1-12 alkyl or phenyl group or modification product thereof).
In another preferred embodiment of the second ink of the invention, the absolute value of zeta-potential of particulate pigment at 20xc2x0 C. and pH value of from 8 to 9 in a diluted ink solution obtained by diluting the ink with ion-exchanged water such that the concentration of the foregoing particulate pigment is from 0.001 to 0.01% by weight is 30 mV or more. The adjustment of the pH value can be accomplished by the use of sodium hydroxide and hydrochloric acid.
A further preferred embodiment of the second ink of the invention is an ink for ink jet recording comprising at least a particulate pigment having a sulfur-containing dispersibility providing group chemically bonded to the surface thereof with a treatment containing sulfur, a penetrating agent, and water, characterized in that the amount of the sulfur-containing dispersibility providing group is 10xc3x9710xe2x88x926 equivalent or more per g of particulate pigment, the sulfur-containing dispersibility providing group is a sulfonic acid group (xe2x80x94SO2OH) and/or sulfinic acid group (xe2x80x94RSO2H in which R is a C1-12 alkyl or phenyl group or modification product thereof), and the absolute value of zeta-potential of particulate pigment at 20 C. and pH value of from 8 to 9 in a diluted ink solution obtained by diluting the ink with ion-exchanged water such that the concentration of the foregoing particulate pigment is from 0.001 to 0.01% by weight is 30 mV or more.
 less than Third Ink of the Invention greater than 
The third ink of the invention gives, as a technical constitution for accomplishing the foregoing xe2x80x9cobject (problem) of ink for ink jet recording (first to fourth inks of the invention) according to the inventionxe2x80x9d, an ink for ink jet recording comprising at least a particulate pigment, a penetrating agent, and water, characterized in that said particulate pigment has a sulfonic acid anion group (xe2x80x94SO3xe2x88x92) and/or sulfinic acid anion group (xe2x80x94RSO2 in which R is a C1-12 alkyl or phenyl group or modification product thereof) chemically bonded to the surface thereof and the counter cation of the sulfonic acid anion group and/or the counter cation of the sulfinic acid anion group is selected from the group consisting of alkaline metal ions and monovalent ions represented by the chemical formula (R1R2R3R4N)+ (in R1, R2, R3, and R4 may be the same or different and each represent a hydrogen atom, alkyl group, hydroxylalkyl group or halogenated alkyl group).
In a preferred embodiment of the third ink of the invention, the counter cation of the sulfonic acid anion group and/or the counter cation of the sulfinic acid anion group comprises at least one of lithium ion (Li+), sodium ion (Na+), potassium ion (K+), ammonium ion (NH4+) and alkanolamine cation.
In a further preferred embodiment of the third ink of the invention, the counter cation of the sulfonic acid anion group and/or the counter cation of the sulfinic acid anion group comprises at least Na+ and NH4+. In a still further preferred embodiment of the third ink of the invention, the total amount of alkaline metal ion in the liquid component (vehicle) of the ink is 10,000 ppm or less, preferably 2,000 ppm or less, more preferably 1,000 ppm or less.
 less than Fourth Ink of the Invention greater than 
The fourth ink of the invention gives, as a technical constitution for accomplishing the foregoing xe2x80x9cobject (problem) of ink for ink jet recording (first to fourth inks of the invention) according to the inventionxe2x80x9d, an ink for ink jet recording comprising at least a surface-treated pigment independently dispersible in an aqueous solvent having a sulfur-containing dispersibility providing group chemically bonded to the surface thereof, a penetrating agent, and water, characterized in that there are incorporated one or more selected from the group consisting of oxazolidine-based compound, alkylisothiazolone, chloroalkylisothiazolone, benzisothiazolone, bromonitroalcohol and chloroxylenol.
In a preferred embodiment of the fourth ink of the invention, the oxazolidine-based compound is 4,4-dimethyloxazolidine, alkylisothiazolone is octylisothiazolone and/or methylisothiazolone, and chloroalkylisothiazolone is choromethylisothiazolone the added amount of which is preferably from 0.01 to 0.5% by weight.
 less than Fifth Ink of the Invention greater than 
The fourth ink of the invention gives, as a technical constitution for accomplishing the foregoing xe2x80x9cobject (problem) of ink for ink jet recording (fifth ink of the invention) according to the inventionxe2x80x9d, an ink for ink jet recording comprising at least a particulate pigment having a sulfur-containing dispersibility providing group chemically bonded to the surface thereof with a sulfur-containing treatment, a penetrating agent, and water, characterized in that said penetrating agent is a material having a structure represented by the following general formula (2), an acetylene glycol-based surface active agent, an acetylene alcohol-based surface active agent, 1,2-alkylene glycol and/or glycol ether.
Rxe2x80x94EOn2xe2x80x94POm2xe2x80x94Xxe2x80x83xe2x80x83(2)
wherein R represents a C4-10 alkanol group which is an n-group and/or other isomers; EO represents an ethylene oxy group; PO represents a propylene oxy group, with the proviso that EO and PO are present in the molecule and their order of arrangement are arbitrary; X represents a hydrogen atom or xe2x80x94SO3M (in which M represents a hydrogen ion, alkaline metal, inorganic base or organic amine); and n2 and m2 each represent the number of repetition of EO and PO, respectively, which are each a value averaged over the entire system.
In a preferred embodiment of the fifth ink of the invention, R in the general formula (2) is a butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group and/or decyl group wherein the butyl group is mainly composed of n-butyl group, isobutyl group and/or t-butyl group, the pentyl group is mainly composed of n-pentyl group and/or other isomers, the hexyl group is mainly composed of n-hexyl group and/or other isomers, the heptyl group is mainly composed of n-heptyl group and/or other isomers, the octyl group is mainly composed of n-octyl group and/or other isomers, the nonyl group is mainly composed of n-nonyl group and/or other isomers, and the decyl group is mainly composed of n-decyl group and/or other isomers.
In a further preferred embodiment of the fifth ink of the invention, n2 in the general formula (2) is from 0 to 10, m2 in the general formula (2) is from 1 to 5, and the average molecular weight of the material represented by the general formula (2) is 2,000 or less.
In a still further preferred embodiment of the fifth ink of the invention, the acetylene glycol-based surface active agent and acetylene alcohol-based surface active agent each are 2,4-dimethyl-5-hexyne-3-ol, 2,4,7,9-tetramethyl-5-desyne-4,7-diol, 3,6-dimethyl-4-octine-3,6-diol and/or 2,4-dimethyl-5-hexyne-3-ol, 2,4,7,9-tetramethyl-5-desyne-4,7-diol or 3,6-dimethyl-4-octine-3,6-diol having 30 or less ethylene oxy groups and/or propylene oxy groups added thereto on the average, the 1,2-alkylene glycol is 1,2-(C4-10 alkyl)diol, and the glycol ether is one or a mixture of two or more selected from the group consisting of diethylene glycol mono(C4-8 alkyl)ether, triethylene glycol mono(C4-8 alkyl)ether, propylene glycol mono(C3-6 alkyl)ether and dipropylene glycol mono(C3-6 alkyl)ether.
 less than Process for the Preparation of Second Ink According to the Invention greater than 
The process for the preparation of the second ink of the invention gives, as a technical constitution of the process for the preparation of the ink for ink jet recording according to the invention, a process for the preparation of an ink for ink jet recording which comprises treating the surface of a particulate pigment with a treatment containing sulfur to allow a sulfur-containing dispersibility providing group to be chemically bonded to the particulate pigment, and then mixing the particulate pigment thus treated with a penetrating agent and water, characterized in that the treatment is used in such an amount that the amount of the sulfur-containing dispersibility providing group to be incorporated is 10xc3x9710xe2x88x926 equivalent or more per g of the particulate pigment.
In a preferred embodiment of the process for the preparation of the second ink for ink jet recording according to the invention, the sulfur-containing dispersibility providing group is a sulfonic acid group (xe2x80x94SO2OH) and/or sulfinic acid group (xe2x80x94RSO2H in which R is a C1-12 alkyl or phenyl group or modification product thereof). In another preferred embodiment of the process for the preparation of the second ink for ink jet recording according to the invention, there is provided a step of subjecting sulfonic acid group and/or sulfinic acid group to ionic dissociation in the ink before the addition of the ink solvent.
In a further preferred embodiment of the process for the preparation of the second ink for ink jet recording according to the invention, the absolute value of zeta-potential of particulate pigment at 20xc2x0 C. and pH value of from 8 to 9 in a diluted ink solution obtained by diluting the ink with ion-exchanged water such that the concentration of the foregoing particulate pigment is from 0.001 to 0.01% by weight is 30 mV or more. The adjustment of the pH value can be accomplished by the use of sodium hydroxide and hydrochloric acid.
 less than Process for the Preparation of Third Ink According to the Invention greater than 
On the other hand, the process for the preparation of the third ink comprises allowing a sulfonic acid anion group (xe2x80x94SO3xe2x88x92) and/or sulfinic acid anion group (xe2x80x94RSO2 in which R is a C1-12 alkyl or phenyl group or modification product thereof) to be chemically bonded to the surface of the particulate pigment, and then mixing the particulate pigment thus treated with a penetrating agent and water, characterized in that the counter cation of the sulfonic acid anion group and/or the counter cation of the sulfinic acid anion group is selected from the group consisting of alkaline metal ions and monovalent ions represented by the chemical formula (R1R2R3R4N)+ (in R1, R2, R3, and R4 may be the same or different and each represent a hydrogen atom, alkyl group, hydroxylalkyl group or halogenated alkyl group).
In a preferred embodiment of the process for the preparation of the third ink, the counter cation of the sulfonic acid anion group and/or the counter cation of the sulfinic acid anion group comprises at least one of lithium ion (Li+), sodium ion (Na+), potassium ion (K+), ammonium ion (NH4+) and alkanolamine cation.
In another preferred embodiment of the process for the preparation of the third ink, there are present at least Na+ and NH4+ as the counter cation of the sulfonic acid anion group and/or the counter cation of the sulfinic acid anion group. In a still further embodiment of the process for the preparation of the third ink, the total amount of alkaline metal ion in the liquid component (vehicle) of the ink is 10,000 ppm or less, preferably 2,000 ppm or less, more preferably 1,000 ppm or less.
 less than Ink Set of the Invention greater than 
The ink set for ink jet recording according to the invention gives, as a technical constitution for accomplishing the object (problem) of the foregoing ink set, an ink set for ink jet recording comprising at least a pigment, a penetrating agent and water, characterized in that said pigment is a surface-treated particulate pigment having a sulfur-containing dispersibility providing group chemically bonded to the surface thereof with a treatment containing sulfur and comprises black, yellow, magenta and cyan pigments in combination.
In a preferred embodiment of the ink set for ink jet recording, the black surface-treated pigment is carbon black, the yellow surface-treated pigment comprises one or two or more selected from the group consisting of C.I. pigment yellow 55, 74, 97, 109, 110, 128, 138, 147, 151, 154 and 180, the magenta surface-treated pigment comprises one or two or more selected from the group consisting of C.I. pigment red 122, 202 and 209, and C.I. pigment violet 19, and the cyan surface-treated pigment comprises one or two or more selected from the group consisting of C.I. pigment blue 15, 15:1, 15:2, 15:3, 15:4, 15:6 and 16.
The ink set for ink jet recording according to the invention further comprises orange and green pigments in addition to the foregoing black, yellow, magenta and cyan pigments, totaling 6 color pigments.
In a preferred embodiment of the ink set for ink jet recording comprising 6 color pigments, there are incorporated the foregoing black surface-treated pigment, the foregoing yellow surface-treated pigment, the foregoing magenta surface-treated pigment and the foregoing cyan surface-treated pigment, the orange surface-treated pigment comprises one or two or more selected from the group consisting of C.I. pigment 43 and 36 and the foregoing green surface-treated pigment comprises one or two or more selected from the group consisting of C.I. pigment green 7 and 36.
The amount of the dispersibility providing group in the foregoing surface-treated particulate pigment to be used in the ink set comprising 4 or 6 color pigments in combination is preferably 10xc3x9710xe2x88x926 equivalent or more per g of pigment particle.
 less than Ink Cartridge of the Invention greater than 
The ink cartridge according to the invention gives, as a technical constitution for accomplishing the object (problem) of the foregoing-ink cartridge, an ink cartridge comprising an ink impregnating foam and an ink incorporated in the ink impregnating foam, characterized in that the ink comprises at least a particulate pigment having a sulfur-containing dispersibility providing group provided on the surface thereof, a penetrating agent and water and the content of sulfur in the liquid component in the ink incorporated in the ink impregnating foam is 2,000 ppm or less, preferably 1,000 ppm or less as calculated in terms of SO42xe2x88x92 ion.
In a preferred embodiment of the ink cartridge of the invention, the pigment is carbon black pigment and/or organic pigment and the penetrating agent is an acetylene glycol-based surface active agent, acetylene alcohol-based surface active agent, 1,2-alkylene glycol and/or glycol ether.
In another preferred embodiment of the ink cartridge of the invention, the ink impregnating foam is a urethane foam which is prepared in the presence of an organic metal compound as a catalyst and the amount of the organic metal compound to be added is from 0.01 to 0.2% by weight based on the weight of the urethane foam.
In a further preferred embodiment of the ink cartridge of the invention, the total amount of metallic ions and other polyvalent metallic ions from the organic metal compound catalyst contained in the liquid component of the ink is 800 ppm or less.
The ink cartridge according to the invention is suitable particularly for ink jet recording apparatus.